NONLINEAR-OPTICAL RESPONSES OF C-70-TOLUENE SOLUTIONS

The third-order optical nonlinear response in C-70-toluene solutions w as studied by time-resolved degenerate four-wave mixing at 532 nm. Bot h the rise and decay time of the four-wave mixing signal were measured as a function of laser excitation energy. The observed decrease of th e rise time as excitation intensity increases is attributed to the lar ge singlet-singlet excited state absorption cross section. The decay t ime of the nonlinear response depended on the sample age and laser exc itation and varied from 110 to 650 ps within the range of the various widely diverging published values.